In solid-state image pickup devices, such as video cameras, digital still cameras and cellular phones having camera function, a CCD or CMOS image sensor that is a solid-state image sensor of color image is used. In such a solid-state image sensor, silicon photo diode having sensitivity to near-infrared rays that cannot be perceived by human eye is used in its light-receiving section. For such a solid-state image sensor, it is necessary to make correction of visibility so that a natural color might be obtained when an image is seen with human eye, and an optical filter (e.g., near-infrared cut filter) to selectively transmit or cut rays of specific wavelength region is frequently used.
As such near-infrared cut filters, those manufactured by various methods have been used in the past. For example, in Japanese Patent Laid-Open Publication No. 1994-200113 (patent literature 1), a near-infrared cut filter in which a transparent resin is used as a base material and a near-infrared absorbing dye is incorporated into the transparent resin is described.
Optical filters, such as the near-infrared cut filter containing a near-infrared absorbing dye described in the patent literature 1, are widely known. As a result of earnest studies, the present applicant has found that a squarylium-based dye among near-infrared absorbing dyes is excellent particularly in steepness in absorption and height of visible light transmittance, and has proposed a near-infrared cut filter containing a squarylium-based dye and having a wide viewing angle in Japanese Patent Laid-Open Publication No. 2012-8532 (patent literature 2).
However, since the squarylium-based dye generally has fluorescence in view of its molecular structure, it sometimes generates scattered light during light absorption, and the image quality of camera is sometimes lowered.